Corrosion inhibitor



CORROSION INHIBITOR Loyd W. Jones, Tulsa, kla., assignor to Pan AmericanPetroleum Corporation, a corporation of Delaware No Drawing. ApplicationOctober 1, 1953 Serial No. 383,689

4 Claims. (Cl. 260-4045) This invention relates to inhibiting corrosion.More particularly it relates to inhibitors for most types of cor rosionoccurring in oil wells and associated equipment or combination of thevarious types of corrosion discussed herein. The corrosion inhibitorsalso act as demulsifiers and parallin removing agents. They may also beemployed to clear water-blocked formations.

This application is a continuation-in-part of my copending applicationU. S. Serial Number 288,705 filed May 19, 1952, now U. S. Patent2,756,211. In the parent application a combination of amines andcarboxylic acids as corrosion inhibitors is disclosed. Such amines arealiphatic amines containing at least 10. carbon atoms per molecule.Examples are dodecyl and octadecyl amines. Straight chain primary aminesare preferred. The acid portion is carboxylic in nature and contains atleast 5 or 6 carbon atoms. Preferably this portion is obtained from theliquid phase partial oxidation of normally liquid petroleum fractions.Other acids such as lauric or oleic are also satisfactory.

These salts are unique in that they inhibit corrosion by hydrogensulfide, carbon dioxide, light organic acids, oxygen or combinations ofthese materials. They are also unique in that at least certain of thesalts avoid the usual emulsion and gel problems encountered when saltsof fatty acids are added to oil. Some of the salts also prevent paraffindeposition on metallic surfaces. These salts may be employed in the formof oil solutions for systems in which the liquid is predominantly oil.For systems in which the liquid is predominantly water the inhibitorshould be used in a water dispersible form. In the case of water havinga low salt content, most of the non-ionic water-soluble emulsifiers ofeither the ester or ether type are suitable dispersing agents. If thewater contains considerable salt, then a special class of non-ionicwater-soluble dispersing agent should be employed. This class ofdispersing agent is more particularly described and claimed in mycopending application U. S. Serial Number 335,161 filed February 4,1953. eral, this class of dispersing agent has the formula RXW, whereinR is an aliphatic hydrocarbon radical containing at least 12 carbonatoms, X is an ether type linkage selected from the group consisting ofoxygen and sulfur and W is a water-soluble portion selected from thegroup consisting of polyglycols and polyglycerols containing at least 4other linkages.

If it is desired to introduce inhibitors through the tubing in a well,or to provide a slowly dispersible form in any application, they may beproduced in stick form by use of oil-soluble waxes such as paraffin orof watersoluble binders ,such as gelatin, as more fully described andclaimed in the copending application U. S. Serial Number 288,345 filedon May 16, 1952, by Jack P. Barrett, now abandoned.

The salts are employed in concentrations of about to 50 parts permillion of corrosive liquids in mildly corrosive systems consistingpredominantly of oil. much as 500 parts per million may be employed inhighly In gen-- ice corrosive liquid is predominantly water theconcentration may vary from 10-to 20 parts per million in moderatelycorrosive systems up to about 200 parts per million is highly corrosivesystems. As little as 10 parts per million gives appreciable protectionin both oil and water systems. The inhibitor may be applied continuouslyor intermittently. If applied intermittently the concentration should becalculated on the basis of the entire volume of corrosive liquids towhich the metal surface will be exposed before the next treatment.

While the salts disclosed in the parent application constitute aconsiderable improvement over prior art inhibitors, they are stillsusceptible to improvement in cer-- tain respects. For example, whilethe use of oxidized petroleum acids to form the salt gives a productwhich. usually avoids emulsion formation between water and oil,

in many areas positive demulsifying action is also desired. Whileprevention of paraflin deposition has been noted, a more positiveparaflin-removing action would be desirable in many locations. Also,while amine salts of the oxidized petroleum acids taught in the parentapplication have been found to possess only limited gel forming abilityin oil, the concentration of the'inhibitor which can be added to oilfor" purposses of storage in.

a. convenient liquid form is limited by the high pour point of the oilsolutions. Some pour points are as high as around 40 F., making theiruse in colder areas diflicult. A salt with a decreased gel formingtendency An improved corrosion inhibiting ability closed amine salts arehighly superior compared to inhibitors previously taught in the priorart.

With the above problems in mind,'an object of the' a corrosion inhibitorwith decreased tendency to gelhydrocarbons so that high concentrationsof inhibitors in oil can be handled without encountering excessivelyhigh pour points. A still further object is to provide a corrosioninhibitor which may also be used to remove water blocks from formations.

In general, I accomplish the objects of my inventionby using a salt ofcarboxylic acids produced by the liquid phase partial oxidation ofnormally liquid petroleum fractions and certain highly polar aliphaticpolyamines having two or more amino groups located at one end of atleast one long hydrocarbon chain. .A preferred example of such acompound is the salt of DuomeenT and Alox 425. Duomeen-T is a trademarkof Armour and Company for the highly polar polyamines having the formula'7 In the formula R" is an aliphatic hydrocarbon radical containing fromabout 16 to 18 carbon atoms- Alox 425 is a trademark of the AloxCorporation for a mixture of acids derived from normally liquidhydrocarbons by 'liquid phase partial oxidation.

Patented June 24, 1958 (3 It reduces the interfaciaL tension between oiland water to nearly zero dynes per centimeter.

(4) It tends to remove water from many water-blocked formations. Y Y

(5). It does not act as an emulsifier of oil and water.

(6) It has apositive demulsifying action on emulsions of water and oil.

(-7) It, is a highly effective corrosion inhibitor even compared toother amine salts.

(8) It, prevents deposition of paraffin from oil onto' metallicsurfaces, and there is evidence indicating that it exerts. a positiveparafiin-removing action on paraffin already deposited;

All these properties are attributable. to the strongly polar; natureofportions ofzboththe: amine'and the acid. Sinceboth the; amine.-and-the acidhave strongly polar porti0ns,,thesalt also is:.highly:polar. Being highly polar, these-1t is not-areaclily solvated byoil.Therefore, it has less: tendency 'to form gels in. oilsv than. lesspolar'materials which-aremore highlyxsolvated by.-the: oils. Thisdecreased ;-'gel-.formingtendency in turn: presumably accountsfor'theincreased oil. solubility. It also apparently accounts for the lower.pour point of: oilsolutions. That is,-it' is necessary to. cool oil'solutions of the salt tolower temperatures before gellation' of. thesolution b'ecomessufiicient to prevent pouring.

Having aCmorepolar portion than'nio'st salts, particularlythose of theamines; the. salt of-iDuomeen-T and Alox.425 is more surface. active;Thisxaccounts for the ability to. decrease the interfacial tensionbetween oil and water: -A- direct application. oflthis' property is theremovaLof water frormwater-blockedi formations of oil wells; When:thesalt, preferably. in' oil solution, isinjected into-suchformationstheinterfacialzforces between water and oilare reducedtosuch'anextnt that theyare insuf- Thehighly polarzsalt is: probablyadsorbed on metallic surfaces to. someextent. It'is niuch more likely,as'pointed' out in.the parentapplication referred to above, thattheamine and acid portions of. the loosely-bound saltare separatelyadsorbed on difierent'portions of the surface. The proposed amine andacid, being more highly polar, become more strongly attached to the:metallic surfaces tobe protected than. the less polar materials;Theincreased.corrosion-inhibiting ability-is due partly to this fact andpartly toi the decreased emulsion-forming tendency. The. probable reasonwhy emulsions decrease the corrosion-inhibiting abilities of most aminesalts is that these salts, being surface active, tend to becomeconcentrated at the large interfacial surface between the liquids ratherthan on the metal surface. When emulsion formation is decreased, more ofthe inhibitor becomes available for deposition on the metal surfaces tobe protected. The reduced-interfacial. tension between oil and wateralso probably facilitates displacement of water fromthemetalsurfaceiby aprotective oil film.

T he strongly-adsorbedhighly polar amine-and'acid' have beenfound toproduce an excellentlubricating film which greatly reduces wear; Inone'pu'mping well, use ofthe salt has already extended by a factor of'5or 6"the average period between pumping rod-pulling jobs. In the well,the corrosion problems were minor, but perhaps just sufiicient toroughen the rubbing surfaces slightly and accelerate wear. to the simplelubricating actions of the strongly adsorbed films on both rubbingsurfaces.

The parafiin-removing ability of the salt may be due to several factors.One of these is an increased paraffinsolubilizing power of the polyaminesalt compared to salts of monoamines. The solubilizing power of thesalts has been demonstrated in connection with the Alex 425 acids. Theseacids are not completely soluble in oil. The oil-insoluble materials areprobably hydroxy acids. Whatever the nature of the materials, however,they are apparently drawn into oil solutions by a solubilizing action ofthe amine salt. It has been observed that the polyamines are moreeffective in solubilizing these oil-insoluble constituents of Alox 425acids. Therefore, they are undoubtedly also more effective insolubilizing materials such as parafiin. Another factor which mayaccount for increased paraifin removing ability is the presence ofalcohols, ketones,esters. and the like in Alox 425 acids. Thesematerials are fair'paraflin 'solvents. Since twiceas much" acid isrequired to neutralize Duomeen-T as is required to neutralize? octadecylamine, for example, more of the alcohols, ketones and esters which.accompany the Alex 425 acids are present when the polyamine salt isemployed. These solvents probably contribute in some degree to theimproved paraffin-removing ability of the polya'mine salts of Alox 425acids.

The principal explanation of the. paraffin-removing ability probablylies in the reduced interfacial tension between oil and water,'and. theconsequent demulsifying action. It has been noted many times thattheparafiin deposited in a well is generally-associated'with:considerablequantities of water.- Where little'water: is present, parafiindeposition is. rarely aproblemi' Apparently it is. an emulsion ofpjarafiin and..waterwliichneposits: The amine-acid salt, by breakingthis" emulsion causes its removal from wellswhere it is deposited."

When the term sa1t'is" employedwithmeference to a process, the termmeans either thepreferred reaction product or. the product formed insitu by use of the amine and acid separately. While the neutral salt isgenerally preferred, as much as twice the stoichiometric amount ofeither the amine or acidmay be presentand most of the advantages willstill be retained.

The acids used in forming the salts of my invention are those producedby the process described in U. S.- Patents 1,690,768 and 1,690,769issued to'Burwell. The hydro carbon feed to the oxidation process for"producing the itcid sd should be a petroleumfraction which is normallyiqui class of hydrocarbons is preferred'since it produces acids in thedesired molecular weight range containing from about 5 to about 20carbon atoms per molecule. Hydrocarbons of a' paraffinic naturearepreferred as feed stock to the oxidation process since they producealiphatic acids having straight chains which align themselves to giveclosely-packed protective films.

In general, it is preferred to oxidize the hydrocarbon to such an extentthat two phases separate. The lower phase has a higher content of acidswhich are superior for purposes of my invention, probably because of thepresence of hydroxyl groups which make these acids much more polar innature. Due to their higher polarity they are less oil-soluble and lesssusceptible to removal by oil from surfaces on which they have beendeposited. Furthermore, their salts with polyamines aremore' polar, andhence more surface activeand less strongly solvated by oils. Althoughthe highly oxidized acids are preferred, those produced by a lightoxidation of a normally liquid petroleum..fraction produceunique'non-emulsifying salts with polyarnines; Salts'of theselightly-oxidized acids also possess some of the same powers of reducinginterfacial tension and removing parafi'in possessed by salts of thehighly oxidized acids, 'but to a lesser degree.

The reduced, wear might also be due- Kerosene is the preferred rawmaterial; This The preferred polyamine is Duomeen-T. Othersatisfactorypolyamines from Armour and Company are Duomeen-S and Duomeen-C. In'Duomeen-T the' long hydrocarbon chain is derived from tallow acids and,hence, most of these chains are saturated. In Duomeen- S, on the otherhand, most of the hydrocarbon chains are unsaturated since they arederived from soy bean oil acids.

With Duomeen-C, the acids are derived from coconut oil and constitute amixture of saturated and unsaturated acids. Most of the hydrocarbonchains in Duomeen-T and Duomeen-S contain from 16 to 18 carbon atoms.

Since coconut oil is made up of acids having a wide range of molecularweights, the resultingamines have a correspondingly varied range ofchain lengths, for example from about 8 to 18 carbon atoms. As indicatedin the parent application previously referred to, a hydrocarbon radicalof at least carbon atoms should be present. Such radicals insure theformation of. a film of sufficient thickness on the metal to resistpenetration even by combinations of corrosive materials such as oxygenand hydrogen sulfide. The straightchain aliphatic hydrocarbon radicalsare very much preferred to insure closer packing of the moleculesforming the film. However, other hy-' drocarbon radicals having at leastabout 10 carbon atoms are also effective to a smaller degree.

The polar portion of the amine should contain at least two amino groupsseparated by from 2 to 4 carbon atoms. This portion may be heterocyclicin nature but preferably should be aliphatic since the salts of thenon-cyclic aliphatic polyamines have surprisingly superior corrosioninhibiting abilities compared to salts of the cyclic polyamines.

So far as I have been able to determine, the aliphatic polyaminespreferred in my invention may best be repre; sented by the formula:

In this formula R is a hydrocarbon radical, preferably aliphatic,containing from about 10 to '20 carbon atoms, N is a nitrogen atom, X isa radical selected from the group consisting of R, H and-RNHY, R is ahydrocarbon radical containing from 2 to 4 carbon atoms, H is a hydrogenatom and Y is a radical selected from the group consisting of H and R.The Duomeens are members of this class, having the simplified formula:

RNHR'NH The preferred amine is Duomeen-T havingthe formula:

R"NH(CH2)3NH2 As previously noted, R" in this formula is an aliphatichydrocarbon radical containing from about 16 to .l8.carbon atoms.

The principal application of the disclosed salts is as inhibitors forcorrosion by oxygen, hydrogen sulfide, carbon dioxide, carboxylic acidscontaining from 2 to 4 carbon atoms per molecule, or combinations ofthese individual corrosive materials. One or more of these materials, orcombinations thereof, occur in various types of oil Wells. In treatingsuch wells it is recommended that at least about 5 parts of thecorrosion inhibitor be added per million parts of well liquids,including both water and oil. This concentration should be used whetherthe inhibitor is added in slugs, for example once a day or so, or isadded continuously. Preferably, a preliminary period of treatment athigher concentrations up to 50 times the suggested steady rate should beemployed for a week or so at the beginning of the treatment. If the oilwell produces predominantly oil, an oil solution of the inhibitor shouldbe added. If the well produces more than about 50 percent water, then awater-dispersible form of the inhibitor may be added. Such a form isdescribed more fully and claimed in my copending application U. S.

Serial Number 335,161, previously noted. Although a treatment .of 5parts per million produces appreciable protection which is, in manycases, quite adequate, for.

more severe corrosive conditions higher concentrations in the range of10 to 50 or more parts per million may be used. In general, higherconcentrations are required for systems consisting predominantly of oilthan for systems which are substantiallyoil-free. The concentrations forpreventing wear should be the same as those for inhibiting corrosionsince the problem in both cases is to establish a protective film.

If wells have been treated, auxiliary field equipment such as flowlines, separators and the liquid space of tanks vapors such as theinsideof casing and outside of tubing near the tops of wells, the vapor spaceof tanks or gas itor and an oil such as kerosene, be sprayed into thevapor space in an amount equal to about 1 gallon of solution perthousand square feet of metal surface to be protected.

The film which is formed in this manner can then be 7 maintained byinjecting smaller amounts of from /2 to ,5 the volume of the originaltreatment at intervals of from about one week to one month, dependingupon the severity of corrosion and erosion by flowing gases.

Another field application of the inhibitor is in drilling fluids toinhibit oxygen corrosion of drilling equipment, particularly the drillpipe. Concentrations of inhibitors should be approximately the same asfor oil well treatments. Since the drilling fluid is recycledcontinuously, addition of inhibitor is necessary only to make up for theamount lost into the formations or on bit cuttings sepa-v rated from thedrilling fluid. A similar application tested with considerable successwas concerned with prevention of corrosion of the ballast tanks onsubmersible drilling barges. This also suggests the application to anymarine vessel into which air-containing water is occasionally.

introduced.

Excellent slushing compounds can be prepared by adde ing the inhibitorto the greases or gels normally employed for this purpose. H Theinhibitor may also be employed in refinery operaof exchangers,condensers or'the like, it is simply injected into the inlet to theequipmentpreferably in oil solution if the system is predominantly oil,and in a water-disper- Siblefortn if the system isipredominantlyaqueous. If the inlet material is a vapor, spraying of the inhibitorinto The inhibitor, being non-volatile, will then runthe stream as a fogis the preferred nretlffodof'injecti' Asfin other applications,introductionof'ithe inhibitor 8. geniq al, however;..I prefertoem'plbyapetroleum fraction such asfkero nc since; cost; is'fmuch lessand the eftec tiv'en'essf is substantially the same;

iilventic'in'will be beitte'r' understood from consideration ofe'followingfexamplesz ning of treatment of refinery equipment shoulcllbeafron; a about 50 to 200 parts per million by weight'of" iqui anvapors treated. After a preliminary treatment at these E Bconcentrations; to establish inhibiting films, the concen? Tojdetejrminef the effectivenessas a corrosion inhibitor nation canusually be reduced over a periodof tinieft'o a of the roposed salt ofD'uomeen'e-T and Alex 42 5"acid's, value as low as about 5 parts permillion, or even lbwer ll! comparedtosaltsdffother amines andacids, thefollowin exceptional cases. It will be understood that when ing testswere conducted. Into l-liter glass bottles reference is made torefineries, the term is employed 800ml. ofanaqueousjpercent'sodiumchloride brine' broadly to include all petroleum processing equipmentwereintroduc'ed;together: with. about 16-rnl'. of kerosene such asnatural gasoline plants; sulfur'removin'g installa} containing variousamounts, of the individual salts in-; tions or dehydrating apparatus; l3dicated ingTable I. Polishedgandtar'ed mild steel test If the amine-acidsalt is employed as a demulsifier, it panels, 1 inch by 1 inch" byfiginch, were suspended in should preferably be introduced into thew'ell'producing thebrine by metal' rods'f fromwhich" the panels wereinthe emulsion. In this way it can act on the water'and' oil"sula't'edby plastic washers." The'ro'ds were suppo'rted', in.atthe'bottom' of the well, thus preventing'ifirmation of turn; by-instigifiintb tlri rubber stoppers employed to the emulsion. At the sametime, theamineacid'salt'acts; close the bottles. A stream" of corrosivegases" was. to prevent corrosion and parafiih depositioni Itis'ip'osbubbled co'ntin ii'ouslythrough theliquids in the bottles sible,however, to add the salt'to' the emulsionafter it is at a latent aboutcubic foot per hour, while thc'tern; formed by injecting it into flowline's, separators; tajnks perature 'wasmaintained art-100 F. Thecorrosive gases. or the like. The amount' of salt. used as" ahemulsifierconsisted of '2 percenthydrogen sulfide and 98 percentair. depends onthe severity of emulsion in each case; In 35 The bottles were shaltnvigorously forv 15 consecutive general, however, it'is suggested'tha'tconcentrationsin the minutes every two hours. the end of 7 days, therange of 2 to 4 or 5 times those suggested forinhibiting panels weredipped 1n dllute inh bited hydrochloric" acid corrosion should beemployed. solution' rubbed lightly to remove adhering scaleg. rinsed Theamine-acid salt may be used to remove paraffin. in distilledwaterifdried and; weighed. The results are from two locations in a well.One' location isthe inside 39 presented in Table I;

Table I e sh L a 1 Coneoi Grams Percent V Amine" Add salt, Inhlbi-Remarks p. p. m. tion, Av.

Control Inhibited ArmeenHT Alox'425: s00 ggggg} 98.0 emulslmi q l. ew: ndo' 100 8%? 81822 94.8 if f pitting-8nd. etch Duomeen-T "do.-." 300 991dN0 emulsion, uniform-protcction.

Do 100' 31%}, 8:88;? 99.0 Do.

Do Oleic 0 g 92,1 Thick emulsion, panels etched,

wall of the tubing through which. the oil flows to thesur- A m HT is atrademark of Armour and Company face. The other is the pore spaceofformations through for a mixture of about 70 percent octadecyl amine andwhich oil flows to the well. Forreinovingparaffin from ab 30 pehexadecylamine DuomeeneT and" inside tubing, the salt may be added' in,thgsameways as Alox 425 have been previously identified chemically.suggested' for inhibiting corrosion. It h s Bri f ii d The greatlydecreased emulsifying tendency of the A10): that the concentrations ofsalt suggested for inhibiting 425 acid salts is to be noted. The salt ofAlex 425 acids corrosion a'r'e suitable for removin paraffin wherepar he is particularly outstanding n a aflin problems are not too serious.Higher concentra' caused no emulsion at all, even at higherconcentrations. tions, in the range of 2' to 4 or 5' times as great, aresug- This particular salt is also outstanding in that s h i gested formore serious cases of parafiiri deposition in il'lg D 1 P- is p il 300P: P- 0f bi the salt of monoamines suchas Armeen-HT.

For removing paraffin from pore spaces, a solution, EXAMPLE H preferably111 a petroleum fractlonsuch as kerosene, con: mining from about 0-001 0Percent 111016" (i0 To compare the effectiveness of Alex 425 salts ofalicf the filming-acid Salt Should be P p to the formflphatic polyaminesto salts of cyclic polyamines, static tion and then be allowed to flowback out. A volume b ttl tests-were" nd ed as f ll 015 501115011suficlcifint t0 fill the P 5 to a One-liter fior'ence flasks" wereflushed free of air by fian Of a ast about 4 r 5 t uld b i j streams ofnitrogen; Into-each flask approximately 1 liter The treating cyclfi y bei m r times of air-free 5 percent sodium chloride brine containing witheither fresh or previously-used solution. Paraflin known amounts ofhydrogen sulfide was introduced; The solvents such as carbontetrachloride, carbon disulfi'dm corrosion inhibitor to be tested wasthen introduced, dis benzene the like y be P Y as a Solvent fOr thesolved inSOml. of kerosene. A tared polished mild steel= salt, but sincepetroleum fractions are so eifective, use of p test panel, 1 inch by 1inch. by inch, was then lowered the more expensive solvents is rarelyjustified'. 0 into each flask, supported by a glass hook which was inWhen a water block is to be removed from a formaturn held by the rubber.stopper used to seal the flask. tion, the procedure, concentrations andvolumes should Eachpanel washeld in the oil layer 5 seconds at the-startbe substantially the same as when parafiin is removed of the testandthen exposed to the brine phase for the from the pore space. Thesolvent for the salt maybe. 75 remainder of the- 7-day test: Results arereported in? a water solvent such as ethanol, acetone orthe like.

Table II.

Table ll I Weight Loss, Salt IDS Grams Percent Amine Cone, Conc.,Inhlbi- Remarks p. p. m. p. p. m. tion, Av.

Control Inhibited 0.0267 0. 0007 Uniform protection. Dumeen T 0. 03430.0007 No emulsion. 0.0263 0018 Slight local attack Z-HeptadecylImldazoline 200 600 0.0266 0'0016 93.7 and pitting. Some 2H td 11H d n11I emulsion' -epaecy-yroxyey .2

Imidazoline. 200 600 0.0266 8-8813 94.1 Do.

Although the concentration of the Duomeen-T salt of Alex 425 acids wasonly one-half those of the corresponding salts of the cyclic imidazolinederivatives, the degree of protection was superior. It will also benoted that the protection was uniform, whereas the salts of the cyclicamines permitted some local attack. The tendency of the cyclic aminesalts to form slight emulsions at 200 p. p. m. concentration should becompared to the absence of emulsifying tendency of 300 p. p. 111. of theDuomeen-T salt noted in Example I. It is apparent that while the cyclicpolyamine salts of Alox 425 acids are very good inhibitors, thealiphatic polyamine salts of the same acids are even better in severalrespects.

EXAMPLE III To determine the effectiveness of the Duomeen-T salt of Alox425 acids as an inhibitor for corrosion due to low molecular weightcarboxylic acids and carbon dioxide, the following test was made:

About 1100 ml. of an aqueous percent sodium chloride brine solution wasplaced in each of several 2-liter round-bottomed flasks together withabout 900 ml. of kerosene. A reflux condenser was placed over each flaskand the systems were freed of air by boiling the water while bubbling astream of oxygen-free carbon dioxide through the liquids for a period of2 hours. The rate of carbon dioxide introduction was about 1 cubic footper hour. To the air-free liquids, 500 milligrams of glacial acetic acidwere added (about 500 p. p. m. by weight based on the water phase). Then100 milligrams of the salt of Duomeen-T and Alox 425 acids we're addedto each of two of the flasks. None of the amine-acid salt was added toanother flask used as a control. A polished, tared, mild steel panel wasthen suspended in thewater phase in each flask on a glass rod passingthrough a seal in the flask. A reflux condenser was placed on the flaskand the flask heater adjusted to hold the temperature just at theboiling point of water. For 15 consecutive seconds out of each minutethe panel was'raised into the oil phase. After 24 hours, the panels werecleaned, dried and weighed as described in Example I. The control panellost 0.1500 grams. One of the panels in the flasks containing inhibitorlost 0.0082 grams; the other. lost 0.0020 grams. Thus, the averageinhibition was 96.6 percent complete.

EXAMPLE IV The effectiveness of the Duomeen-T salt of Alex 425 acids wastested as an inhibitor of corrosion of surface equipment of abrine-disposal system in the East Texas field. Corrosion productsindicated the corrosive agents to be hydrogen sulfide and air. The testswere conducted on a surface pipeline from a pump to a'disposal well. Onetest nipple was inserted a few feet downstream from the pump. Anotherwas inserted a few feet upstream from the injection well, situated about/2 mile away. After 31 days exposure to the brine, these nipples wereremoved, cleaned and weighed. A second set of test nipples wassubstituted for the first set and injection of 15 the amine-acidinhibitor was started. The inhibitor was added as a kerosene solutioncontainingA pounds of salt per gallon of solution. It was injectedcontinuously into the pump suction through a small control valve. At-

tempted rates of injection were as follows:

First 3 days-1 quart of solution per 120 barrels brine. Next 2 weekslquart of solution per 240 barrels brine.

Remainder of 32-day test-l quart of solution per 300 barrels brine.

These concentrations should have varied from about 22 p. p. m. by weightdown to about 9 p. p. m. However, to treat the 81,000 barrels of brineaccording to this schedule should have required about '85 gallons of thesolution.

Actually, only 68 gallons were injected because of difli-' Table IIIWeight Loss 40 7 Percent Nipple PosltioninLine Treated Inhibition VGrams Percent Total Nipples 1 and 2 contained sulfide scale and werepitted.

5U Nipples 10 and 20 were clean of sulfide scale and were not pitted. Itwill be apparent'that the air-sulfide corrosion, which cannot beprevented by most inhibitors now on the market,was effectively inhibitedby the proposed amine-acid salt. Examination of the nipples indicatedmost of the inhibitor was deposited near the pump, only traces of theoily material being carried through the line to the nipple near thewell. Much more effective inhibition near the well would undoubtedlyhave been'ootained by use of' the water-dispersible form described andclaimed in my copending application U. S. Serial Nurnher 335,161. v p

' EXAMPLE v Pour points of oil solutions of amine-acid salts were depourpoints melting point of the Duomeen-T undoubtedly accounts in part forsome of the decrease in pour point of solutions or" its salts. However,a decrease of about 30 r. in the melting point of one constituent of thesalt in the solution could hardly be expected to produce a drop in pourpoint of 60 F. in straight oil solutions and 25 F. in the complexwater-dispersible composition. The pour point reduction is particularlyimportant in northern areas where the temperature frequently remains ator below about F. for considerable lengths of time. in such areas moredilute solutions of the water-dispersibie form should be employed. Thepour point of this form can also be reduced further by increasing thealcohol content of'the preparation.

EXAMPLE VI The ability of the salt to break emulsions and prevent theirformation was recently demonstrated in connection with a well in theChocolate Bayou field of Texas. operator was using the salt of Armeen HTand Alex 425 acids as an inhibitor. The salt was added as a kerosenesolution containing about 4 pounds of salt per gallon of solution. Thisinhibitor solution was added at a rateof about 2 quarts per day. Thewell production averaged about 6 to million cubic feet of gas per day,together with about 50 to 100 barrels of condensate and about 1 to 2barrels of water. indicated by a low iron content of the water. theamount of inhibitor employed caused the formation of a slight emulsion.When this emulsion was treated in the laboratory with about 200 to 400parts per million of the Duo mee n-T salt of Alex 425 acids, theemulsion broke immediately, thus demonstrating the ability of thisparticular salt to break even those emulsions causedby other aminesalts. On the basis of this observation, the Duomeen-T salt of Alox 425was employed in subsequent treatment of the well. No further emulsiontroubles have been noted, thus demonstrating the emulsion-preventingability of this salt.

EXAMPLE VII The water-block removing ability of an oil solution of: thesalt of Duomeen-T and Alex 425 acids was determined in the laboratory byuse of a core of Springer sand obtained from a well in the Velma fieldof Oklahoma. The core was drilled with oil, shipped in oil and stored inoil until used in the test. The core tested was drilled from the largecore received, using oil as a lubricant during the drilling. Theresulting test core was a cylinder. having a circular cross-section of2.78 square centimeters and a length of 2.71 centimeters. This core wasmounted in a rubber stopper through which a hole had been bored slightlysmaller than the core. The stopper was, in turn, mounted in a taperedLucite holder to which inlet and outlet connections were made. Variousliquids were forced through the core under a diiferential pressure ofapproximately one atmosphere and at a room temperature of about 75 to 80F. Permeability values were obtained by measuring the volume of liquidflowing out of the core over a short period of time, such as a minute orThe- Corrosion control was good, as However,

12 two, and calculating the permeability which would account for thisrate of flow. was forced through the core, the brine was one prepared bydissolving in fresh water 96,000 p. p. m. by weight of sodium chloride,9,000 p. p. in. calcium chloride and 3,000 p. p. m. magnesium chloride.The hydrocarbon employed for flushing and as a solvent forinterfacial-tem" sion-reducing agents was a narrow-boiling petroleumfraction containing hydrocarbons predominantly in the range having from10 to 12 carbon atoms per molecule. The procedure and results were asfollows:

(l) The permeability of the core to flow of the petroleum fraction wasfirst determined to be millidarcies.

(2) One liter of the brine was forced through the core. The permeabilityof the core to the flow ofibrine at the end of this operation was 164millidarcies.

(3) The petroleum fraction was again introduced and after 616 ml. hadbeen forced through the core, the. permeability to the flow of thehydrocarbon was only 52 millidarcies, showing the core to bewater-blocked.

(4) A solution of a polyoxyethylene sorbitol tetraoleate obtained fromthe Atlas Powder Company under the trademark G-2854 was then forcedthrough the core to remove the Water block. This material is known to Areduce the interfacial tension between Water and oil. solution of 0.05percent by weight in the petroleum fraction was employed; After 173 ml.of the solution had been forced through the core, the permeability toflow of the solution was found to be 179 millidarcies.

(5) The pure petroleum fraction was next pumped through the. core todetermine if the improved permeabil ity was permanent.

the eifiuent hydrocarbon returned to its normal value. The permeabilityto fiow of the petroleum fraction at this time was 153 millidarcies.

(6) The blocking and cleaning steps were repeated, using a second- Atlasinterfacial tension reducer with.

approximately the same results.

(7) The core was again water-blocked by introducing the brine.Permeability to the flow of the petroleum fraction after the blockingoperation was 52.4 millidarcies.

(8) A solution containing 0.001 percent of the 1110- meen-T salt ofA102: 425 acids in the petroleum fraction was then forced through thecore. After 96 ml. had' been introduced, the permeability to flow of thesolution was 53.7 millidarcies.

(9) The concentration of the salt was increased to Permeability,

Volume Through, ml.

Millidarcies (12) Upon flushing the core with the pure petroleumfraction, the permeability increased to 189.5 millidarcies instead ofdecreasing,.as had been characteristic of flushing after treatment withthe Atlas compounds.-

(13) The interfacial tensions between the brine and the petroleumfraction containing various concentrations of the amine-acid salt weredetermined. The results are presented in Table V.

In every case where brine This flushing operation was con-- tinued untilthe interfacial tension between water and After introduction of 167 ml.of this solution,

It will be apparent that the amine-acid salt is somewhat more efiectivethan the non-ionic material for removing water block from formations.The reason for the greater effect is probably a stronger tendency to beabsorbed on the sand grains, resulting in a greater ability to displacethe water. Obviously, the concentration of the amine/acid salt in oilused for removing water blocks should be about 0.05 percent or moresince a sharp increase in permeability occurred when the concentrationwas increased to this value from'the 0.01 percent previously used.

From consideration of the above description and examples, it will beapparent that I have accomplished the objects of my invention. Aconsiderably superior corrosion inhibitor has been provided in thatlower concentrations produce the same or greater uniformity and degreeof inhibition produced by higher concentrations of other inhibitors. Inaddition, the inhibitor exerts a positive demulsifying action, as wellas avoiding the emulsion problems often caused by other inhibitors. Thegel-forming tendency of the inhibitor is so low that high concentrationsin oil can be handled without danger of solidifying in cold weather. Thematerial also acts to prevent paraflin deposition and to remove paraifinwhich has already been deposited. The ability of the salt to removewater blocks has also been demonstrated.

I claim:

1. The salt of a polyamine and a carboxylic acid, said acid beingderived by liquid phase partial oxidation of a normally liquid petroleumfraction and said polyamine having the formula RNH(CH NH wherein R is ahydrocarbon radical containing at least about 10 carbon atoms, and x isan integer from 2 to 4 inclusive.

2. The salt of claim 1 in which said polyamine has the formula R"NH(CHNH wherein R" is an aliphatic hydrocarbon radical containing from 16 to18 carbon atoms.

3. The salt of claim 2 in which said acid is derived by liquid phasepartial oxidation of kerosene.

4. The salt of a polyamine and a carboxylic acid, said acid beingderived by liquid phase partial oxidation of a normally liquid petroleumfraction and said polyamine having the formula RNH(CH NH wherein R is analiphatic hydrocarbon radical containing at least about 10 carbon atomsand x is an integer from 2 to 4 inclusive.

References Cited in the file of this patent UNITED STATES PATENTS2,290,412 De Groote et a1 July 21, 1942 2,303,366 Katzman Dec. 1, 1942,2,583,399 Wachter et al. Jan. 22, 1952 2,587,546 Matuszak Feb. 26, 19522,614,980 Lytle Oct. 21, 1952 2,736,658 Pfohl et a1. Feb. 28, 1956

